Cardiac stimulation systems commonly include a pulse generating device or pulse generator, such as a pacemaker or implantable cardioverter-defibrillator (ICD), that is electrically connected to the heart by at least one electrical lead. An electrical lead provides an electrical pathway between the pulse generator, connected to the proximal end of the lead, and myocardial tissue, in contact with the distal end of the lead. In such a manner, electrical pulses emitted by the pulse generator travel through the lead and stimulate the heart. Intrinsic cardiac signals may be sensed by electrodes located on the lead and conducted via the lead to sense amplifiers in the device for monitoring the heart's natural rhythm.
As implantable electrical devices have increased in their complexity, there have been an increasing variety of electrical lead systems developed for use in conjunction with these devices. Nowhere is this more apparent than in the context of ICDs, which may include two, three or more leads located for sensing or stimulating up to all four heart chambers. The leads themselves may carry one, two, three, or more electrodes, and may employ a variety of different electrical connector configurations and types. As a result, manufacturers of implantable pacemakers and ICDs have had to produce their products with a variety of connector block configurations, capable of use with different lead systems. However, there are standards which must be followed by manufacturers and the present invention is reflective of these standards.
The pulse generator is usually implanted in a subcutaneous cavity, and the leads extend either transvenously to the internal cavities of the heart, or to patch electrodes located on external surfaces of the heart.
The leads generally include at least one electrode located at a distal end and an electrical connector for interconnection to the pulse generator at the proximal end. The connector at the proximal end and the distal electrode are interconnected by at least one conductor extending through an insulated body. It is common, as already mentioned, for the leads to include two or more electrodes and two or more electrical contacts at the connector.
The connector is inserted into a receiving orifice in a header assembly of the pulse generator. The main body of the pulse generator is generally a metallic self-contained hermetically sealed housing or can which encloses the source of electrical energy and electronic circuitry for controlling the electrical stimulus delivered by the lead and isolates the electronic components from the body environment. The header assembly of the pulse generator defining the receiving orifice may be formed from a biocompatible plastic material which conventionally has been formed and bonded to the main body of the pulse generator. It is current practice to fabricate the header assembly of the plastic material, possibly employing the cast epoxy process. For the cast epoxy process, the liquid epoxy consists of two parts which need to be mixed together with very precise proportions. The cast epoxy process is labor intensive and time consuming and it frequently occurs that the epoxy leaks into the connector blocks, requiring its removal or substantial reworking of the assembly.
More recently, attempts have been made to provide pre-formed header assemblies and the present invention is an improvement of this preferred technique.
It was in light of the foregoing that the present invention was conceived and has now been reduced to practice.